The present invention is related to optical networks and, more particularly to, protection and network management measures and procedures in such networks.
When a fault occurs in the transmission of signals from one network component to another network component, such as a break in an optical fiber, protection measures of the optical network cause the rerouting of the signals around the fault to ensure the delivery of optical signals to their destination. There are different ways to protect optical networks against faults. One protection mechanism used in point-to-point links is the 1+1 mechanism in which a source network component sends duplicate signals on two separate fibers to a destination network component. The destination network component which had been accepting the optical signals over one fiber, called the working fiber, switches to the other fiber, called the protection fiber, in case a fault occurs with the working fiber to continue receiving the signals. Another protection mechanism is the 1:1 mechanism (a special case of 1:N protection) in which the source network component sends optical signals over the working fiber to the destination network component. In case of a fault in the transmission, the source network component then switches the transmission of optical signals to the protection fiber. (In the 1:N mechanism there is one protection fiber for N working fibers.)
These protection functions are typically implemented in modules which can be inserted into equipment at different network sites. For WDM (Wavelength Division Multiplexing) systems, specific wavelength bands are defined as communication channels. It should be noted that WDM is used herein in this inclusive sense, rather than in reference to particular standards, such as the ITU (International Communications Union)—defined WDM, DWDM (Dense WDM) and CWDM (Coarse WDM). Hence optical protection modules on either side of network optical amplifiers, which help maintain integrity of the optical signals as they travel long distances through the network optical fibers, can protect all the channels on the fiber spans between optical amplifiers, called optical line sections (OTS). Likewise, optical protection modules at the respective output and input terminals of the multiplexers and demultiplexers of the WDM network, protect all the channels on the fiber spans between the multiplexers and demultiplexers, called optical multiplex sections (OMS). But in any case these sites should be able to communicate with each other for the management, testing and maintenance of such protection functions.
Heretofore such communications have been handled by ancillary network units through out-of-band communication channels, i.e., extra channels set aside for such operations. Such arrangements consume valuable resources. It would beneficial if special equipment and channels set aside for the management, testing and maintenance of protection functions were reduced to a minimum or eliminated altogether. The present invention is directed toward that goal.